Nestable Container

Abstract

A nestable container of thin wall plastic construction having a stacking protuberance in the bottom thereof to limit the extent of telescopic association of adjacent containers. The stacking protuberance comprises a lower stacking shoulder of generally circular configuration, an upper stacking shoulder having an odd number of lobes numbering at least three extending radially outwardly a distance greater than the radius of the lower stacking shoulder, and an intermediate side wall connecting the upper stacking shoulder and the lower stacking shoulder, said side wall having an inclination which varies about the periphery of the protuberance between a convergent angle and a divergent angle with respect to the container axis.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains generally to nestable thin wall plastic containers which incorporate means to prevent adjacent containers in a stack from jamming or sticking together, and more particularly to containers having such means formed in the bottom thereof.

2. Description of the Prior Art

Thin wall plastic containers are widely manufactured for a variety of uses. The containers are generally bowl or cup shaped, having side walls diverging upwardly from the bottom. Such containers are usually molded and, since they are chiefly one-way disposable carriers, the thickness of the material used is in the realm of 0.01 inches. Such containers can be jammed together by the application of telescopic loads, and are easily deformed and damaged by telescopic loads and by abusive handling.

Telescopic forces of sufficient magnitude to cause jamming or sticking can easily be generated during normal manual or automatic handling, thereby inhibiting the removal of individual containers from the top or the bottom of the stack. In the case of automatic machines, such as drink vending machines, the consequence of this jamming or sticking can be the rendering of the machine inoperable. In the case of manual removal of a container from the stack, jamming and sticking causes container damage and waste. To eliminate this problem, means to separate adjacent containers can be molded into each container. These separating means can be in the area of the rim, side wall, or bottom. One form of such means is a pattern of protuberances molded into the sides or the bottom of the container. The use of protuberances in the side wall of a thin wall plastic container renders the outer surface unsuitable for the application of printing, and also eliminates the aesthetically pleasing smooth side wall shape. If the side wall protuberances are inwardly facing, a recess is created in the outer surface, and this recess collects dust and dirt.

An alternative is the use of bottom stacking protuberances. Bottom stacking protuberances of many configurations are set forth in the prior art, as shown in U.S. Pat. Nos. 2,988,258; 3,027,596; 3,131,845; and 3,442,420. The protuberance must be operationally effective no matter what the relative radial alignment of adjacent containers. For example, a protuberance cannot be of such configuration as to nest with an adjacent protuberance when a telescopic load is applied, thus defeating their purpose.

The protuberance must also be easily molded and removed from the mold. In U.S. Pat. No. 2,988,258 the concept advanced is the use of at least two different easily moldable configurations of bottom stacking protuberances so that adjacent containers can be provided with protuberances of dissimilar configuration. This solves the problems of nesting of adjacent protuberances, but greatly complicates the operations of molding and packaging. The other three patents cited above utilize bottom stacking protuberances which include an intermediate wall having an undercut or back-draft portion connecting the upper and lower stacking shoulder. Thus, an engaging shoulder is created on the top of one protuberance to engage the bottom of the adjacent container. However, the use of backdraft angles raises serious problems in the molding operation. Where back-draft angles are radially oppositely aligned, a pinching action is exerted on the mold portion which formed the protuberance, thus inhibiting removal of the container from the mold. This can increase the wear on the mold, lower the operating speed of the machine, and cause damage to the containers. To solve this problem, certain prior art devices utilize a back-draft at a single portion only of the protuberance, but this is generally unsatisfactory, as discussed below.

It is desirable to distribute the telescopic load evenly upon the bottom of each individual container to prevent the possibility of damage due to forces being concentrated at a single point. If a single back-draft is used, all of the telescopic force is concentrated at a single point, often exceeding the strength of the container at that point or causing the container to wedge sideways and, if adjacent protuberances happen to be radially aligned, one protuberance will be forced to nest over the other.

Another consideration in the design of bottom stacking protuberances is to provide minimum intrusion into the volume of the container while maintaining the effectiveness of the protrusion to prevent jamming and sticking. It is also desirable for the protuberance to be aesthetically pleasing, as well as not interferring with implements used to remove the contents from the container.

The bottom stacking protuberances set forth in the prior art, as exemplified by the cited patents, fall short of solving the problems enumerated above.

SUMMARY OF THE INVENTION

The invention advanced herein provides a novel bottom stacking protuberance which eliminates or greatly reduces the effects of the abovementioned problems. A thin wall plastic container manufactured in accordance with this invention has a side wall extending upwardly and diverging outwardly from a bottom into which is installed a stacking protuberance. The stacking protuberance has a lower stacking shoulder and an upper stacking shoulder, both disposed symmetrically about the container axis. The upper stacking shoulder describes an odd number of radially outwardly extending lobes numbering not less than three. The upper stacking shoulder can also form the periphery of an upper surface parallel to the container bottom. A protuberance wall connects the lower stacking shoulder and the upper stacking shoulder. At the outer portions of the lobes, the upper stacking shoulder extends outwardly from the container axis a radial distance greater than that portion of the lower stacking shoulder which is radially aligned therewith, preferably by a degree of at least the thickness of material of which the container is formed. This creates an engaging portion on the upper stacking shoulder and the upper surface which will engage the bottom of an adjacent protuberance, and which will exist even if adjacent protuberances are of identical radial alignment. The protuberance wall varies in inclination with respect to the container axis about the periphery of the upper stacking shoulder, and is divergent with respect to the container axis at each of the engaging portions of the lobes. Therefore, the protuberance wall has a back-draft portion at each upper stacking shoulder lobe.

Removal of a container constructed in accordance with this invention from the mold is facilitated by the novel arrangement of back-draft portions so that they are not directly opposed, thereby allowing the container to easily and safely deform as necessary during removal from the mold without damage and without the application of a high level of force.

Telescopic forces placed upon containers constructed in accordance with this invention are distributed symmetrically over a large portion of the bottom of the container, thus preventing sideward shifting of the container under telescopic load and lessening the chance of damage. Since a plurality of symmetrical engaging portions is provided by this invention, nesting of protuberances of identical radial alignment under the influence of telescopic loads is precluded.

It is an object of this invention to provide a thin wall container having a novel bottom stacking protuberance that prevents adjacent containers from jamming or sticking together under the influence of telescopic loading.

Another object of this invention is to provide a thin wall container having a novel bottom stacking protuberance that facilitates removal of the container from the mold.

Another object of this invention is to provide a thin wall container having a novel bottom stacking protuberance that distributes telescopic loads symmetrically over a large portion of the bottom of the container.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary perspective view showing a seamless thin wall plastic container having a bottom stacking device in accordance with the present invention;

FIG. 2 is a top view of the container of FIG. 1;

FIG. 3 is a cross-sectional view taken through line III--III of FIG. 2;

FIG. 4 is a cross-sectional view of the relationship of protuberances of adjacent containers constructed in accordance with this invention; and

FIG. 5 is a top view of another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The general form of cup or container 10, which incorporates the bottom stacking means of the present invention, is illustrated in FIGS. 1-3 of the drawings. Container 10 is of a seamless thin wall construction molded from a thermoplastic material such as polystyrene, and formed into a frustoconical shape including a bottom 12 and a peripherially continuous side wall 14, which diverges upwardly and outwardly from bottom 12 and terminates in a rim portion 11. The container illustrated is an example only, for the bottom stacking protuberance herein set forth can be utilized equally well with containers of other shapes and of other materials.

A novel stacking protuberance 18 is integrally formed into bottom 12 by conventional thermoforming techniques. As best illustrated in FIG. 3, stacking protuberance 18 comprises a lower stacking shoulder 13, an upper stacking shoulder 15 axially spaced from lower stacking shoulder 13, and a protuberance connecting wall section 16. Although stacking protuberance 18 is illustrated as being inwardly directed, it could also be outwardly directed within the scope of the invention.

Lower stacking shoulder 13 is in the plane of bottom 12, and is symmetrically disposed about container axis 17. Lower stacking shoulder 13 is illustrated as having a circular configuration of radius R1, but other configurations can be used within the scope of this invention.

The upper stacking shoulder 15 is advantageously in a plane parallel to the plane of bottom 12, and describes a plurality of lobes 21. In the practice of this invention, lobes 21 can be of any odd number not less than three. Upper stacking shoulder 15 lies about the periphery of an upper surface 20, which can be in the same plane thereas. Portions of upper stacking shoulder 15 extend radially outwardly beyond that portion of lower stacking shoulder 13 radially aligned therewith. In the case of a circular lower stacking shoulder 13, these portions of upper stacking shoulder 15 extend outwardly a radial distance greater than Radius R1, and an engaging portion 22 which contacts the bottom of an adjacent container is defined on surface 20 upper stacking shoulder 15. Upper stacking shoulder 15 also describes indented portions 19 spacing each of lobes 21 from one another. Indented portions 19 are of lesser or equal radius than lower stacking shoulder 13 radially aligned therewith. The maximum radial distance R2 from axis 17 to upper stacking shoulder 15 at engaging portions 22 preferably exceeds that of the radially aligned point of lower stacking shoulder 13 by at least the thickness of the material from which the container is constructed. This insures the presence of sufficient overlap between the protuberance of adjacent containers to prevent nesting of adjacent protuberances. In this embodiment, as shown in FIG. 2, surface 20 is configured somewhat like a three leaf clover. However, it is not necessary that lobes 21 be three in number, but only that an odd number of lobes, not less than three, be utilized. The lobes can be arcuate or of other configuration, such as the one shown in FIG. 5.

Lower stacking shoulder 13 is illustrated as being of circular configuration, but that is not a necessity. The chief requirement is that the radial distance R2 of upper stacking shoulder 15 at engaging portions 22 must exceed the radial distance R1 of that portion of lower stacking shoulder 13 which is radially aligned therewith. The remainder of the periphery of upper stacking shoulder 15 is of radial distance less than or equal to the radial distance of the respective radially aligned portion of lower stacking shoulder 13.

A protuberance side wall 16 connects upper stacking shoulder 15 and lower stacking shoulder 13. Since engaging portions 22 are of greater radial distance from axis 17 than the portion of lower stacking shoulder 13 radially aligned therewith, side wall 16 varies in inclination between an angle A diverging from axis 17 at engaging portions 22, and an angle B which converges toward axis 17 at the remainder of the periphery of upper stacking shoulder 15. Although illustrated as alternating portions of simple curvature, resulting in a distinct joining line 23 at each lobe 21, side 16 can be of compound curvature, thus presenting a continuous smooth line.

The maximum convergent inclination of side 16 will vary depending upon such factors as the height of the protuberance and the desire for minimum intrusion into the volume of the container. In the container illustrated, the maximum convergent angle B is about 37 degrees from the vertical. Portions of protuberance wall 16 not radially aligned with engaging portions 22 can be parallel to, rather than converging upon, axis 17. Thus, as illustrated, angle B can be vertical. As angle A, the back-draft, is increased at engaging portions 22, the area of each engaging portion 22 is increased. It is normally desirable to utilize a minimum angle of back-draft, consistant with the design effectiveness of the protuberance.

As shown in FIG. 4, adjacent containers are prevented from jamming or sticking due to the engagement of a portion of bottom 12a of the upper container 10a with engaging portions 22 of the lower container 10. No matter what the relative radial positioning the lobes 21 of the two protuberances 18 and 18a, all of the engaging portions 22 will contact bottom 12a.

Owing to the symmetrical lobular pattern, the upper container 10a is supported at three equally spaced points in a plane parallel to bottom 12 no matter what the radial orientation of one container to the other. Thus, loads transmitted from container to container are distributed to a large portion of the bottom of the container, and are not concentrated at a single area.

Removal from the mold is facilitated by the presence of symmetrical back-draft portions opposite which there is a portion of wall 16 having no back-draft.

The height of protuberance 18 should be held to a minimum to minimize the loss of container volume attributable thereto. The height H selected for protuberance 18 is dependent upon the divergence of sides 10, the thickness of the material of which the containers are formed, and the desired separation between the sides 10 of adjacent containers. Since the stacking protuberance 18 provided by the instant invention is symmetrical about the container axis 17, telescopic loads will be evenly transmitted between adjacent containers and the possibility of containers tilting to the side opposite the engaging shoulder under load is eliminated. Likewise, deformation of the container in one direction and nesting of protuberances over one another is eliminated.

It should be noted that the particular configuration of protuberance 18 which is shown in FIG. 2 is not critical to the invention. For example, as shown in FIG. 5, upper stacking shoulder 35 can describe a protuberance 38 of equilateral triangle configuration having engaging portions 42 at the corners thereof. Protuberance 38 is symmetrically disposed about the container axis 37. In this configuration, lower stacking shoulder 33 is also of generally triangular shape. The radial distance from the container axis 37 to upper stacking shoulder 35 at the corners exceeds slightly the radial distance to the portion of lower stacking shoulder 33 which is radially aligned therewith. Engaging portion 42 are thereby created at the corners. In this configuration there are three areas of engagement. Side wall 36 varies in inclination in the same manner as explained above with reference to the other illustrated embodiment, having back-draft angles at each of the engaging portions 42.

The exact configuration of the protuberance can vary greatly within the limits of the invention. The embodiments set forth above include but two of the many usable configurations. The number of lobes can also be varied within the parameters set forth above. Therefore, the inventive concept is extremely versatile and can be used with many container types, designs, and materials.

Obviously, many variations and modifications of the invention described above will become obvious to those skilled in the art. However, the scope of the invention is not to be governed by the embodiments illustrated herein, but is to be determined by the claims.

Claims

We claim:

1. In a thin wall plastic container having a bottom and a side wall extending upwardly and outwardly from said bottom, a stacking protuberance disposed symmetrically about the axis of said container comprising:

a lower stacking shoulder in the plane of said bottom;

an upper stacking shoulder axially spaced from said lower stacking shoulder and parallel thereto, said upper stacking shoulder describing an odd number of lobes numbering not less than three symmetrically disposed about said axis;

a protuberance wall connecting said lower stacking shoulder and said upper stacking shoulder, said protuberance wall having an angle of inclination divergent in an upwardly direction with respect to said container axis at the outer portions of each of said lobes to form an engaging portion on each of said lobes to engage the bottom of an adjacent container; and

indented portions of said upper stacking shoulder spacing said lobes from one another, said protuberance wall having an angle of inclination convergent in an upwardly direction with respect to said container axis at said indented portions which are located diametrically opposite each of said lobes.

2. A container according to claim 1 wherein said lower stacking shoulder is circular and said lobes and said indented portions are arcuate.

3. A container according to claim 1 wherein said upper stacking shoulder describes a substantially triangular configuration, said lobes being the corners thereof.

4. A container according to claim 1 wherein said upper stacking shoulder forms the periphery of an upper surface in the plane of said upper stacking shoulder.